1. Field of the Invention
The present invention relates to a current detector for detecting a current flowing in an electric circuit mounted on an equipment such as an automobile or the like, and particularly to a current detector which can increase a current detecting accuracy, and an electric connection box using the same.
2. Description of the Prior Art
Conventionally, there has been known a current detector for detecting a current flowing in an electric circuit, for example, mounted on an automobile by using a Hall element corresponding to one of magnetic-electric conversion elements. One example of this kind of current detector is disclosed in Japanese Patent Application Laid-Open No. 5-223849. The current detector is provided, as shown in FIGS. 1A to 1C, with a conductor 1 forming a loop-shaped current path 1b by applying notches 1a on the same plane or bending so as to flow a current to be detected I, and a magnetic-electric conversion element 2 converting a magnetic flux generated by the current to be detected I flowing through the conductor 1 into an electric signal.
In this current detector, the current to be detected I flows through the loop-shaped current path 1b formed in the conductor 1, whereby the magnetic flux is generated. The magnetic flux is converted into the electric signal by the magnetic-electric conversion element 2, whereby an electric signal in proportion to magnitude of the current to be detected I can be obtained. Since this current detector senses two times or more magnetic flux in comparison with the case that the electric-magnetic conversion element is placed near a straight conductor, it is possible to increase an accuracy of detecting the current.
However, in the current detector disclosed in Japanese Patent Application Laid-Open No. 5-223849, since the magnetic flux generated by the current flowing through the conductor body except the conductor to be measured becomes a disturbance and gives an influence to a detected result, there is a problem that it is impossible to accurately detect the current flowing through the conductor to be measured.
An object of the present invention is to provide a current detector which can accurately detect a current flowing through a conductor to be measured and an electric connection box using the electric detector.
The present invention is structured as follows in order to achieve the object mentioned above. According to a first aspect of the present invention, there is provided a current detector comprising: a conductor to be measured in which a through hole is formed, the conductor to be measured having a first branch path and a second branch path for dividing a current flowing into two portions; a first magnetic-electric conversion element being arranged in the through hole of the conductor to be measured, the first magnetic-electric conversion element being provided for detecting a disturbance; and a second magnetic-electric conversion element being arranged outside of the first branch path and the second branch path formed in the conductor to be measured.
According to the invention, the current flowing through the conductor to be measured flows through the first branch path and the second branch path in a diverged manner. In this case, since a direction and a magnitude of the current flowing through the first branch path is the same as those of the current flowing through the second branch path, the magnetic flux generated by the current flowing through the first branch path and the magnetic flux generated by the current flowing through the second branch path have the same strength and opposite directions at a position of the through hole.
As a result, since both of the magnetic flux deny together at the position of the through hole, the first magnetic-electric conversion element arranged in the through hole outputs zero if a magnetic flux other than the magnetic flux on the basis of the current flowing through the conductor to be measured (hereinafter, refer to as xe2x80x9ca disturbance magnetic fieldxe2x80x9d) does not exist. This means that the first magnetic-electric conversion element outputs an electric signal corresponding to a strength of the disturbance magnetic field.
On the other hand, since the second magnetic-electric conversion element is arranged outside the first branch path or the second branch path, the second magnetic-electric conversion element outputs an electric signal corresponding to a strength of a combined magnetic field between the magnetic field generated by the current flowing through the first branch path and the magnetic field generated by the current flowing through the second branch path. At this time, if a disturbance magnetic field input to the second magnetic-electric conversion element exists, the second magnetic-electric conversion element outputs an electric signal corresponding to a strength of a magnetic field obtained by combining the disturbance magnetic field with the combined magnetic field.
Accordingly, for example, when a correction is performed so as to remove the electric signal from the first magnetic-electric conversion element from the electric signal from the second magnetic-electric conversion element, the corrected electric signal accurately reflect the magnitude of the current flowing through the conductor to be measured, so that it is possible to accurately detect the current flowing through the conductor to be measured.
Further, according to a second aspect of the present invention as it depends from the first aspect, there is provided a current detector, wherein the second magnetic-electric is arranged on the same plane as a plane including the first branch path and the second branch path and arranged outside both of the first branch path and the second branch path.
According to the invention, since the second magnetic-electric conversion element is arranged on the same plane as the plane including the first branch path and the second branch path formed in the conductor to be measured and outside the first branch path or the second branch path, each of the magnetic flux generated by the current flowing through the first branch path and the magnetic flux generated by the current flowing through the second branch path substantially vertically passes through a magnetic sensing surface of the second magnetic-electric conversion element, so that a greater electric signal is output, whereby a higher sensibility can be obtained.
According to a third aspect of the present invention as it depends from the first or the second aspect, there is provided a current detector further comprising: a correction portion for correcting an electric signal output from the second magnetic-electric conversion element on the basis of another electric signal output from the first magnetic-electric conversion element.
According to the invention, the correction portion corrects the electric signal output from the second magnetic-electric conversion element on the basis of the electric signal output from the first magnetic-electric conversion element. The correction can be performed, for example, in such a manner as to remove the electric signal from the first magnetic-electric conversion element from the electric signal from the second magnetic-electric conversion element. As a result, since the electric signal output from the correction portion accurately reflects the magnitude of the current flowing through the conductor to be measured, it is possible to accurately detect the current flowing through the conductor to be measured.
According to a fourth aspect of the present invention, there is provided an electric connection box, comprising: a plurality of conductors being arranged substantially in parallel to each other; and a current detector, wherein the current detector comprises: a conductor to be measured which is made of any one of the plurality of conductors being arranged substantially in parallel to each other by being formed with a through hole, the conductor to be measured having a first branch path and a second branch path for dividing a current flowing into two portions; a first magnetic-electric conversion element being arranged in the through hole of the conductor to be measured, the first magnetic-electric conversion element being provided for detecting a disturbance; and a second magnetic-electric conversion element being arranged outside of the first branch path and the second branch path formed in the conductor to be measured.
According to the invention mentioned above, since the current detector is provided in the electric connection box in which a plurality of conductors are arranged, any one of a plurality of conductors is set to the conductor to be measured, the through hole is formed in the conductor to be measured, and the first branch path and the second branch path for dividing the current flowing by the through hole into two portions are formed in the conductor to be measured, the magnetic flux generated by the current flowing through the first branch path and the magnetic path generated by the current flowing through the second branch path deny together at the position of the through hole, so that the first magnetic-electric conversion element outputs the electric signal corresponding to the strength of the disturbance magnetic field. On the contrary, the second magnetic-electric conversion element outputs the electric signal corresponding to the strength of the magnetic afield obtained by further combining the disturbance magnetic field with the combined magnetic field between the magnetic field generated by the current flowing through the first branch path and the magnetic field generated by the current flowing through the second branch path.
Accordingly, for example, when a correction is performed so as to remove the electric signal from the first magnetic-electric conversion element from the electric signal from the second magnetic-electric conversion element, the corrected electric signal accurately reflect the magnitude of the current flowing through the conductor to be measured, so that it is possible to apply the current detector which can accurately detect the current flowing through the conductor to be measured to the electric connection box.
According to a fifth aspect of the present invention as it depends from the fourth aspect, there is provided an electric connection box, wherein the other conductor except the conductor to be measured among the plurality of conductors is arranged in such a manner that a distance between the other conductor and the first magnetic-electric conversion element is substantially equal to a distance between the other conductor and the second magnetic-electric conversion element.
In accordance with the invention mentioned above, since the conductors except the conductor to be measured among a plurality of conductors are arranged so that the distance between the conductor and the first magnetic-electric conversion element is substantially equal to the distance between the conductor and the second magnetic-electric conversion element, each of the first magnetic-electric conversion element and the second magnetic-electric conversion element is affected by the magnetic field from the conductor in a substantially uniform manner. Accordingly, when the correction is performed in such a manner as to remove the electric signal from the first magnetic-electric conversion element from the electric signal from the second magnetic-electric conversion element, the corrected electrical signal is not affected by the magnetic field from the conductor at all, so that it is possible to obtain an accurate current detecting value.